On Mon, Sep 19, 2016 at 10:58:56PM +0200, Olaf Schreck wrote: > > Check ip neigh output. Does the entry for your default gateway go > > STALE after those 20 minutes? > > Yes, exactly: > > # ip -6 nei > fe80::1 dev eth0 lladdr 0c:86:10:ed:31:ca router STALE
So it is the neighbor table entry going stale. Does your system retry neighbor solicitation (see tcpdump) or does it sit quietly with a STALE entry? I had this behavior in similiarly styled hosting networks a few years ago, and since it has fixed itself I suspect a kernel issue that was fixed since then. I do use more recent kernels than Debian stable though. > > Do you really need to meddle with the fe80::1 route? > > I had no plans to do so. I just learned during debugging that this would > reestablish IPv6 connectivity without reboot. It would be interesting to see whether this causes your system to do a neighbor solicitation for the default gateway. > > Do you really > > need an explicit route for fe80::1%eth0? Will it work without? > > My hosters docs (Hetzner) recommend that. They don't specify an IPv6 > default gateway. They're unfortunately not very clueful with regard to IPv6. I haven't been on their network for years though. > > or is it > > really necessary to remove the default route and to re-add it? > > yep, connectivity is back Interesting. > > No need, an fe80::/64 IP address is only valid when an interface is > > added: > [...] > > Is the other interface connected? eth1 should not play a role here at > > all. > > I had no plans to fiddle with link-local addresses, and of course eth1 > settings should not matter. I just disabled IPv6 on eth1 for debugging, > and suddenly IPv6 worked >20min. Maybe coincidence rather than causality. Check whether your system re-solicits for the default gateway with eth1 down and/or up. If its re-solicitation behavior on eth0 differs depending on eth1's state, we have a clear system software issue here. If we're not talking about jessie but something more recent, systemd-networkd might play a role. systemd-networkd has recently started to take over IPv6 mechanics, and does so in a quite broken way. > I'd like to learn what's going on here, Me too > thanks for your comments. You're welcome Greetings MArc -- ----------------------------------------------------------------------------- Marc Haber | "I don't trust Computers. They | Mailadresse im Header Leimen, Germany | lose things." Winona Ryder | Fon: *49 6224 1600402 Nordisch by Nature | How to make an American Quilt | Fax: *49 6224 1600421
